The present disclosure relates to a fixing device fixing a toner image on a sheet and an image forming apparatus including this fixing device.
An image forming apparatus includes a fixing device fixing a toner image formed on a sheet. The fixing device includes a fixing member heating the toner image formed on the sheet, and a pressuring member pressuring the toner image to the sheet. The fixing device applies, for example, a fixing belt as the fixing member and, inside the fixing belt, a nip forming member sandwiching the fixing belt together with the pressuring member to form a fixing nip between the fixing belt and the pressuring member and a supporting member being anchored to a fixing frame and supporting the nip forming member are provided.
For example, a conventional fixing device includes a belt member provided circulation-movably, a pressing member coming into contact with an outer circumference face of the belt member to press the belt to an inner side, a receiving member arranged so as to come into contact with an inner circumference face of the belt member to receive pressing force from the pressing member, and a supporting part supporting the receiving member. The supporting part has one end at an upstream side in moving direction of the belt member and the other end at a downstream side in the moving direction, is arranged so as to face to the receiving member, and includes a first piece receiving a load from the receiving member. The supporting part includes a second piece connected to a one end side of the first piece to go to in a separating direction from the receiving member, and a third piece connected to the other end side of the first piece to go to in a separating direction from the receiving member. The supporting part includes a fourth piece arranged so as to have a gap between the first piece and the fourth piece and connected to the second piece and the third piece. The supporting part includes an anchored member anchored to the first piece and the fourth piece and having a portion arranged between the second piece and the third piece.
In the fixing device, the supporting member receives pressuring force from the pressuring member via the nip forming member. If the supporting member is deformed by the pressuring force, because pressure distribution brought to the fixing nip by the nip forming member becomes uneven, the supporting member needs to be made with sufficient strength. If the supporting member is made of wide sheet metal in order to improve strength of the supporting member, it is necessary to sure a large space for anchoring the supporting member to the fixing frame and size of the other members located around the supporting member is restricted. Moreover, if the supporting member is made by bending the sheet metal multiple times in order to improve strength of the supporting member, it is difficult to accurately form an attached face of the supporting member on which the nip forming member is attached. If the inaccurate nip forming member is attached to an inaccurate attached face, pressure distribution of the fixing nip becomes uneven.
Incidentally, in the fixing device, the fixing belt is rotatably attached to the supporting member. For example, caps are attached to both ends of the fixing belt and pivot supporting members pivotally supporting the caps rotatably are attached at both ends of the supporting member. The pivot supporting members need to be positioned to the supporting member in a rotating direction and a circumference direction of the fixing belt, and to be fastened to the supporting member. However, because the supporting member cannot apply much processing on the reason of strength improvement, a shape of the pivot supporting member is restricted according to a shape of the supporting member.